1. Field of the Invention
The present invention relates to a radio communication apparatus, a radio communications system, and a radio-communications method based on IEEE 802.11, especially supporting virtual LAN.
2. Description of the Background
IEEE 802.3 is a well known standard for communicating on a wired LAN, and IEEE 802.11 is a well known standard for communicating on wireless LAN. They are established by the IEEE (Institute of Electrical and Electronics Engineers, Inc.).
IEEE 802.3 is a standard generally known as “Ethernet”™. According to this standard, “Ether frame” packets are transferred between wired terminals in 60-1514 bytes per second.
On the other hand, IEEE 802.11, which is a standard for the wireless LAN, has several versions (e.g. IEEE 802.11a, IEEE 802.11b, and IEEE 802.11g). There are differences in communication frequency and transfer rate between them.
IEEE also recommends IEEE 802.1Q relating to a VLAN (Virtual LAN). IEEE 802.1Q can be used together with IEEE 802.3 and IEEE 802.11. A VLAN includes two or more virtual local area networks built in a network.
Moreover, IEEE 802.11i for communication security is also recommended. IEEE 802.1Q defines a security mechanism with encrypting transferred data based on IEEE 802.11.
However, the security mechanism of IEEE 802.11i cannot work in the VLAN of IEEE 802.IQ because security parameters of IEEE 802.11i are selected based on a destination MAC (Media Access Control) address of the Ether frame.
For example, a terminal that can receive a multicasted or broadcasted Ether frame destined for a MAC address of another terminal that belongs to a VLAN may also be able to receive Ether frames destined for other VLANs.
If an encryption key of first a VLAN is different from encryption keys for other VLANs, a terminal that belongs to one of the other VLANs cannot interpret an Ether frame that is destined for the first VLAN. However, that terminal of the other VLAN also cannot recognize Ether frames sent as part of a third party attack or by mistake. Thus, a terminal that supports IEEE 802.11i cannot fulfill the requirements of IEEE 802.1Q VLAN.
As an attempt to solve this problem, JP-A-2004-200812 describes a method to provide new session information on multicast communication to provide security between multicast groups.